This invention relates to a device for transporting sheetlike material between a conveyer belt and a guide means each lying against one of the two opposite sides of the material. Such devices are used in particular in paper conveying technology for example in printing machines, copiers, document processing machines and the like as well as in bank note processing machines.
In the field of bank note transport it is known for example from DE 43 02 827 A1 to transport bank notes between two transport belts moving equally fast and in the same direction. This transport method firstly involves an elaborate and high-maintenance belt guiding system and regularly requires a great number of belt deflection points to transfer sufficiently strong clamping power to the bank notes in order to convey them in frictional engagement. To improve adhesion between the circulating conveyer belts, DE 43 02 827 A1 proposes disposing means for causing magnetic and/or electromagnetic forces. Such an arrangement quite obviously involves considerable effort and energy consumption and moreover very quickly leads to problems of electromagnetic interference. Furthermore, one must also expect problems with the sensors used therein, in particular when used in bank note testing devices.
It is known from DE 28 57 883 C2 to convey bank notes between a transport belt and a fixed plate. Such a device has in particular the disadvantage of tending to crinkle or jam the bank notes due to the one-sidedly applied high friction on the stationary wall.
A further problem occurring with conveyance by transport belts is the undefined clamping power the belt exerts on the bank notes to be conveyed in particular when bank notes of varying thickness are conveyed at short distances one behind the other. For example, if a thin bank note is located between two clearly thicker bank notes regarded in the transport direction, a much lower frictional force is transferred to this thinner bank note than to the two adjacent thicker bank notes.
For conveying sheet material it is also known from DE 29 14 969 A1 to transport the sheet material between a row of firmly mounted rollers and a further row of spring loaded rollers. Such an arrangement has the disadvantage that the sheet material is unguided on both sides in the area between two pairs of rollers so that crinkling or jamming can easily occur.
The invention is therefore based on the problem of providing a device for transporting sheetlike material which guarantees a reliable transport function even at high conveying speeds and with fluctuating sheet thickness while being of simple structure and easy to maintain.
This problem is solved by a device according to claim 1.
The inventive solution is characterized in particular in that the sheetlike material is guided areally by the conveyer belt on the one hand, while the latter always ensures sufficient pressing force between sheet material and conveyer belt by reason of the elastic action of the pressure elements.
It is advantageous with respect to wear and energy consumption if the pressure elements are formed as pivotally mounted rollers. It is particularly suitable to use rolling bearings, which require little maintenance and are also especially cost-effective being standard parts.
For guidance and elastic bias of the pressure elements it is particularly suitable to use leaf springs since they can perform both functions with minimal effort and fitting space.
A preferred embodiment of the invention provides that the guide means is a roller train with pivotally mounted rollers. In particular if very great fluctuations in the sheet thickness of the transport material are to be expected, it is advantageous if the roller train consists of rollers elastically acted upon in the direction of the conveyer belt. This permits part of the fluctuation in thickness of the sheet material to be compensated by the motion of the pressure elements and the remaining part by the displacement of the guide means.
The pressure elements and the rollers of the roller train are preferably disposed opposite each other in pairs. Especially good guidance of the transport material is obtained if the roller train has cylindrical rollers since this results in linear clamping action on the transport material, thereby reliably maintaining the given transport direction.
An embodiment of the invention which is particularly easy to maintain and to operate provides that the conveyer belt and guide means, on the one hand, and the pressure elements, on the other hand, are each disposed in a portion of a hinged frame.
It has a supporting effect on transport safety if the device has a transport channel into which both the conveyer belt and the guide means protrude. Said transport channel preferably covers the maximum sheet format to be conveyed and ensures that disturbing influences are kept away from the transport path, especially in the area of the side edges of the sheets where there is a danger of dog ears forming.